In 336 AD, the Roman Empire was under the rule of Emperor Constantine the Great, who is known for being the first Roman emperor to convert to Christianity. This year is significant as it marks the death of Constantine, who played a crucial role in the spread of Christianity throughout the empire and established Constantinople as a new capital. Additionally, 336 AD is notable for the establishment of the Christian calendar, which later became widely used in the Western world. The year also saw the continuation of various political and military challenges within the empire, as well as the ongoing interactions between different cultures and religions.